The present invention claims the benefit of Korean Patent Application No. P2001-28756 filed in Korea on May 24, 2001, which is hereby incorporated by reference.
1. Field of the Invention
The present invention relates to a display device and method of fabricating the same, and more particularly to a liquid crystal display device and a fabricating method thereof, and a reworking method of alignment film using the same.
2. Discussion of the Related Art
In general, a liquid crystal display device controls light transmissivity of liquid crystal molecules by application of an electric field, thereby displaying an image. The liquid crystal display device includes a liquid crystal display panel where liquid crystal cells are arranged in a matrix configuration, and a driving circuit is provided for driving the liquid crystal display panel. The liquid crystal display panel has a common electrode and pixel electrodes for applying an electric field to each of the liquid crystal cells. Generally, the pixel electrodes are formed on a lower substrate within liquid crystal cells and the common electrode is formed on an entire surface of a upper substrate. Each of the pixel electrodes is connected to a switching device such as a thin film transistor (TFT), for example, and together with the common electrode, drive the liquid crystal cell according to a data signal supplied through the TFT.
FIGS. 1 and 2 show a liquid crystal display device according to the conventional art. In FIG. 1, the conventional liquid crystal display device includes a black matrix 32 that is sequentially formed on an upper substrate 11, an upper plate UG comprising a color filter 30 and a transparent electrode 28, a TFT that is formed on a lower substrate 1, a lower plate DG comprising a pixel electrode 22, and a spacer 26 formed for preparing an inner space to have liquid crystal molecules injected between the upper plate UG and the lower plate DG. The black matrix 32 is formed on the upper substrate 11 in matrix configuration to divide a surface of the upper substrate 11 into a plurality of cell areas. Color filters are formed in each of the plurality of cell areas to prevent light interference between adjacent cell areas. Color filters 30 of red, green and blue are sequentially formed on the upper substrate 11 where the black matrix 32 is formed. Accordingly, each of the color filters 30 is formed by spreading a material, which absorbs white light and only transmits light of a specific wavelength, i.e., red, green or blue, on an entire surface of the upper substrate 11 where the black matrix 32 is formed, and then patterning the material. A material for forming the transparent electrode 28 is spread on the upper substrate 11 where the black matrix 32 and the color filter 30 are formed, thereby completing the upper plate UG.
In FIG. 2, on the lower plate DG, the TFT that drives the liquid crystal cell is formed at an intersection of a gate line 2 and a data line 4. The pixel electrodes 22 overlap adjacent portions of the gate line 2 and the data line 4 that are arranged in a matrix configuration formed on the lower substrate 1.
FIGS. 3A-3E show a fabrication process of a portion of the liquid crystal display device along A-Axe2x80x2 of FIG. 2.
In FIG. 3A, a gate metal film is formed on a lower substrate 1, and then patterned to form a gate line 2 and a gate electrode 6.
In FIG. 3B, an insulating material is deposited on an entire surface of the lower substrate 1 for covering the gate line 2 and the gate electrode 6, thereby forming a gate insulating film 12. First and second semiconductor materials are sequentially deposited on the gate insulating film 12, and subsequently patterned, thereby forming an active layer 14 and an ohmic contract layer 16.
In FIG. 3C, a data metal film is formed on the gate insulating film 12, and then patterned, thereby forming a data line 4, a source electrode 8, and a drain electrode 10. The ohmic contact layer 16 is then etched exposing a channel portion of the active layer 14. The channel portion of the active layer 14 corresponds to the gate electrode 6 between the source electrode 8 and the drain electrode 10.
In FIG. 3D, a protective film 18 of an organic material is deposited on the gate insulating film 12 and then planarized using spin coating technique, The protective film 18 is then patterned, thereby forming a contact hole 20 exposing a portion of the drain electrode 10.
In FIG. 3E, a transparent conduction material is formed on the protective film 18, and then patterned, thereby forming a pixel electrode 22 that is electrically connected to the drain electrode 10 via the contact hole 20. An alignment film 24 (of FIG. 1) is formed on an entire surface of the lower substrate 1 where the pixel electrode 22 is formed. A rubbing process is performed to complete the lower plate DG. Next, as shown in FIG. 1, the upper plate UG and the lower plate DG are bonded together with a spacer 26 of spherical shape positioned along a periphery therebetween. Finally, liquid crystal molecules are injected in a cavity between the bonded upper and lower plates UG and DG, thereby completing the liquid crystal display device.
However, after formation of the protective film 18, a significant amount of time passes before the pixel electrode 22 is formed, and contaminants are absorbed by the surface of the protective film 18. Accordingly, the alignment film 24 is poorly formed on the contaminated surface of the protective film 18.
FIG. 4 shows the result of a poorly formed alignment film 36 on a contaminated surface of a protective film 18. Accordingly, processing is performed for reworking the poorly formed alignment film 36 using a dry-etching technique.
FIG. 5 shows the result of performing the rework processing. First, the lower plate DG is mounted in a chamber, and O2, O2+Cl2, CF4, SF6 gases are injected into the chamber, thereby generating a plasma discharge. Then, the alignment film 36 is etched to be completely removed from the pixel electrode and protective film 18 by reaction between the injected gas and the alignment film 36. However, because the alignment film 36 and the protective layer 18 have similar dry-etching rates, the protective film(18) becomes over-etched in regions A. Accordingly, since the rework processing of the alignment film causes over-etching of the protective film 18, device yield and productivity are significantly decreased.
Accordingly, the present invention is directed to a liquid crystal display device and a fabricating method thereof, and a reworking method of alignment film using the same that substantially obviates one or more of the problems due to limitations and disadvantages of the related art.
An object of the present invention is to provide a liquid crystal display device and a method of fabricating the same where an alignment film having irregularities or defects may be removed without effecting an underlying material layer.
Another object of the present invention is to provide a method of reworking an alignment film of a liquid crystal display device.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, a liquid crystal display device includes a substrate, an organic insulating film formed on the substrate, an alignment film having a first etch rate formed on the organic insulating film, and a silicon nitride layer having a second etch rate formed between the alignment film and the organic insulating film, wherein the first etch rate is different from the second etch rate.
In another aspect, a method of fabricating a liquid crystal display device includes forming an organic insulating film on a substrate, forming an alignment film having a first etch rate on the organic insulating film, and forming a silicon nitride layer having a second etch rate between the alignment film and the organic insulating film, wherein the first etch rate is different from the second etch rate.
In another aspect, a method of reworking an alignment film of a liquid crystal display device includes forming an organic protective film on a substrate, forming a silicon nitride layer having a first etch rate on the organic protective film, forming a first alignment film on the silicon nitride layer, detecting at least one irregularity of the first alignment film formed on the silicon nitride layer, eliminating the first alignment film with a second etch rate different from the first etch rate of the silicon nitride layer, and forming a second alignment film on the silicon nitride layer.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.